Reactivating lead-contaminated catalysts



United States Patent 6 Filed dept. 19, 1966, Ser. No. 56,795

The present invention relates to the regeneration or reactivation of catalytic contact masses which have become contaminated with lead as a consequence of exposure to contact with lead-containing waste products incident to the catalytic conversion of such :waste products; and, in particular, the present invention concerns the regeneration of catalysts employed in the conversion of the exhaust gases emanating from an internal combustion engine using leaded fuel.

it is now recognized that the elimination of certain components present in automotive exhaust gases is highly desirable and of prime importance in protecting the public health and welfare. The unavoidably incomplete combustion of hydrocarbon fuels by the gasoline or diesel engine results in the generation of substantial quantities of unburned hydrocarbons and other undesirable materials which, as waste products, are released to the atmosphere through the exhaust line. With the ever-increasing concentration of automobiles, particularly in urban areas, the discharge of such Waste products into the atmosphere may reach significantly deleterious proportions. These combustion products are believed to react With atmospheric oxygen, under the influence of sunlight, to produce what is now commonly referred to as smog. Such combustion products include, by way of example, unsaturated hydrocarbons, partially oxidized hydrocarbons such as alcohols, ketones, aldehydes and acids, etc., carbon monoxide, and various oxides of nitrogen and sulfur. Although at least a portion of these compounds may be partially removed by chemical sorption media, the conversion of exhaust gas constituents by catalytic means is by far the preferred technique. The desired objective is to achieve substantially complete conversion of all of the unburned hydrocarbons, particularly the high molecular weight unsaturated hydrocarbons, and carbon monoxide, as well as the partially-oxidized hydrocarbons hereinabove set forth, into carbon dioxide and water prior to discharging the exhaust gases into the atmosphere. Gasoline powered internal combustion engines are a major but not the only source of atmospheric pollution; others include diesel engines, propane or butane engines, natural gas engines, fired heaters, flare stacks, and the like.

Catalytic means for improving waste products for discharge into the atmosphere, and particularly for the conversion of the hydrocarbonaceous combustion products contained within the exhaust gases emanating from an internal combustion engine, necessitate the use of a catalyst possessing an exceptionally high degree of activity, and particularly stability or capability of performing its intended function for an extended period of time. A wide variety of factors affect the stability of active catalytic composites, which factors are generally peculiar to the environment in which the catalyst is employed. In regard to catalysts for the conversion of hydrocarbonaceous combustion products emanating from an internal combustion engine, the actual operation of the engine must be considered. For example, such engine is commonly operated over a wide range of speed and load conditions and, therefore, the combustion efficiency thereof correspondingly varies; the space velocity and temperature of the exhaust gases, as well as the concentration of combustible material therein, likewise vary over wide limits. The catalyst should be capable of withstanding high tempera- 3,117,935 Patented Jan. 14, 1964 "ice tures of the order of 1600 F. to as high as 2000 F. without rapid thermal deactivation, and preferably should possess maximum activity at substantially lower temperatures. The catalyst should have a relatively low threshold-activation temperature in order that the conversion reactions be self-initiating within a minimum time following startup from relatively cold conditions. In general, it is desirable that the catalyst be satisfactorily active at temperatures within the range of about 200 F. to about 2000" F.

The catalyst is usually disposed as a confined particleform bed disposed in a suitable container or catalytic convertor which is installed in the engine exhaust line. The catalytic convertor may be of the through-flow, crossfiow, or radial-flow design and, in the case of vehicular applications, may supplant or be combined with the usual acoustic mufiier. In the majority of systems, secondary or combustion air is injected upstream of the catalytic conversion zone, usually by means of an aspirator or by external compressor means.

Although a great many potentially good, high activity catalysts have been developed which perform well even under the aforesaid adverse conditions, such catalysts are nevertheless deleteriously affected by lead and lead compounds which are present as vapors or as entrained solids in the exhaust gases resulting from the combustion of a leaded fuel. The majority of motor fuels, including some fuels for marine engines, contain tetra-ethyl lead or equivalent lead compounds as an additive for increasing the anti-knock efficiency of the engine in which the fuel is consumed. A typical commercial tetraethyl lead additive contains, in addition, approximately 2 gram-atoms of chlorine and 1 gram-atom of bromine, usually as ethylene dihalide, per gram-atom of lead, which is thus 1.5 times the stoichiometric quantity of halogen required to form the lead dihalide; in conventional terminology, the tetraethyl lead additive is said to contain 1.5 theories of halogen. The halogen serves as a scavenging agent to prevent buildup of lead deposits on spark plugs and engine cylinder walls by preferentially converting the lead tetraethyl, under the elevated cylinder temperatures prevailing during combustion, to highly volatile lead halides, for example, to lead chloride and lead bromide or to the oxyhalides of lead; minor quantities of lead do not react with halogen and are converted instead to less volatile lead oxides. The major proportion of these lead compounds are discharged, as vapors or fines, into the exhaust line along with the exhaust gases. When the resulting lead-contaminated exhaust gases pass into contact with the exhaust gas conversion catalyst, the stability of the catalyst is substantially impaired, which phenomenon is demonstrated by the fact that the catalyst deactivation rate is very much greater than when unleaded fuel is employed.

On its face, this result would appear quite anomalous ince most of the lead enters the conversion zone as a halide, and the normal catalyst bed temperature is in the range of 500 F. to 1600 F. whereby such halide is readily volatilized, whence one would expect the lead halide to pass completely through the bed with as much facility as it escaped deposition upon the engine cylinder walls and exhaust manifold structure. Such, however, is not the case. Although various theories have been proposed to explain the deactivation of catalysts by lead, it appears that the principal mechanism by which catalyst poisoning or deactivation occurs is one of chemical reaction between the volatile lead compounds and the catalyst base whereby to yield a stable, relatively non-volatile lead compound-catalyst base complex which plugs the pores of the catalyst and/or forms a mono-molecular film of complex over the entire micro-structure of the catalyst; evidence favors the latter theory because, in most instances, physical measurements of spent lead-contaminated catalyst reveal no appreciable reduction in surface area or pore volume as against those of the fresh catalyst. By catalyst base is meant a refractory inorganic oxide carrier or support, preferably of medium to high surface area, with which one or more catalytically active metals are composited. Typical bases include, for example, alumina, titania, silica, alumina-silica, aluminazirconia, alumina-silica-zirconia, and the like. The deactivation of the catalyst is believed to proceed via the following reactions which are exemplary but not exhaustive of the several interactions of lead compounds with catalyst bases:

(2) MeOH MeOPbXSMeOPbOMe +HX (3) MeoPbX-i-H OsMeOPbOH-l-HX where Me represents an equivalent of a metallic component of the catalyst base, e.g., Al, Zr, Ti, etc. and X is a halogen, for example, chlorine, bromine or iodine. Water, in the vapor or superheated vapor state, enters into Reactions 3 and 4, supra, which water is inevitably present in hydrocarbon combustion products. When the catalyst accumulates an average lead content within the range of 5% to 30% by weight, and, more commonly, to by weight, which may occur after anywhere from 1000 to 20,000 road miles of operation, depending upon the presence or absence of catalyst guard media, average space velocity, concentration of lead in the fuel, physical and/or chemical properties of the catalyst, and various other factors, the hydrocarbon and carbon monoxide conversion activities of the catalyst have usually fallen to such a low value as to preclude continued use, and such lead-contaminated catalyst must therefore be replaced with fresh catalyst or regenerated.

Experimental data have shown that when a catalyst is exposed to contact with a preponderance of plumbiferous gases, the lead content of the catalyst eventually stabilizes at an equilibrium level, usually in the range of from about 10% to about 25% by weight of lead, in a manner somewhat analogous to the deposition of coke upon cracking catalyst in a fluid catalytic cracking unit with resultant attainment of equilibrium catalyst.

The instant invention has for its principal objective a method of regenerating a lead-contaminated catalyst, and is founded upon the discovery that the conversion activity of such spent catalyst may be substantially restored by contacting the catalyst with an aqueous solution of a synthetic detergent, particularly the anionic detergents characterized by the aryl-sulfonates, and the alkali metal alkylsulfates, as well as the cationic detergents or invert soaps, and the non-ionic detergents.

Prior art methods of regenerating a lead-contaminated catalyst have been concerned with more or less complete removal of the lead by treating the catalyst with strong reagents such as nitric acid, hydrochloric acid, aqua regia, acetic acid, and the like. However, these reagents will also attack, by Way of dissolution or oxidation or both, many of the components most beneficially employed in oxidation catalysts such as alumina, magnesia, titania, zirconia, copper, silver, gold, the iron group metals and oxides thereof, and to a lesser extent the platinum group metals; while the removal of lead may be substantially complete, there often results the concurrent loss of valuable catalytic constituents and/ or an adverse chemical or physical change in the treated catalyst.

The detergent solution of the instant invention, on the other hand, has proven extremely advantageous in that it causes no appreciable loss of catalytic constituents; further, while the detergent solution may in some cases effect the removal of only a minor portion of the lead, surprisingly the oxidation activity of the regenerated catalyst is nevertheless virtually completely restored.

The precise effect of the detergent solution upon a lead compound-catalyst base complex is not known, it is established, however, that improved catalytic activity and any substantial degree of lead removal are not necessarily concomitant. For this reason it is believed that the detergent solution converts the several lead compound-catalyst base complexes to a form or forms of lead which exert a substantially lessened deactivating effect upon the catalyst. While in some instances it is possible to accomplish more or less complete removal of lead from the catalyst by practice of this invention, it should be emphasized that such lead removal is not necessary to the successful utilization thereof. The instant method is, of course, applicable to regeneration in situ and to external regeneration.

In one embodiment, the instant invention relates to a method of regenerating a lead-contaminated catalyst which comprises subjecting said catalyst to contact with an aqueous solution of a synthetic detergent, and more particularly with an aqueous solution of an anionic synthetic detergent such as an arylsulfonic acid, or salt thereof separating said catalyst from the solution and drying the catalyst.

A more specific embodiment of the present invention provides a method of at least partially restoring the oxidation activity of an oxidation catalyst comprising from about 0.01% to about 10% by weight of a noble metal and in major proportion an inorganic refractory oxide base, such catalyst having become substantially deactivated by exposure to plumbiferous exhaust gases under oxidation conditions, which method comprises subjecting said catalyst to contact with an aqueous solution containing anions of an aryl sulfonic acid, separating said catalyst from the solution, water-washing the catalyst, and calcining the catalyst at a temperature above about 800 F.

The method of the present invention and the benefits afforded through the utilization thereof will be more clearly understood by defining several of the terms employed within the specification and the appended claims. The term catalys or oxidation catalyst is intended to connote an element, compound, composite of two or more elements or compounds, or mechanical mixture of elements, compounds or composites which are employed for their catalytic activity in regard to the oxidative conversion of various waste products, particularly hydrocarbons and/or carbon monoxide. The terms lead, leadcontaining and lead-contaminated refer to metallic lead, lead compounds, particularly lead salts such as the sulfates and halides thereof, lead oxides, lead oxyhalides, mixtures of two or more such lead compounds, leador lead salt-catalyst complexes etc., since the actual form or forms in which the lead may exist in the exhaust gases or in combination with the catalyst are not definitely known and, in any event, are of no consequence to the operability of the present method.

It is understood that the instant method of catalyst regeneration is applicable to a great mmy catalysts, and the invention is not therefore to be limited to utilization or regeneration of any one catalyst or class of catalysts.

Typical conversion catalysts to which the present invention may be applied comprise one or more catalytically active metallic components which are preferably composited with a refractory inorganic oxide carrier material. Suitable catalytically active metallic components include,

- but are not limited to, vanadium, chromium, molybdenum, tungsten, members of the iron group and platinum group of the Periodic Table, copper, silver and gold. A particular metal may be used singly or in combination with any of the foregoing metals. Thus, the catalyst may comprise metals selected from groups 1B, VA, VIA and VIII of the Periodic Table. Especially desirable catalytically active metals or combinations thereof comprise the following: platinum, palladium, other noble metals such as iridium and rhodium, iron, cobalt, nickel, chromium, copper, vanadium, tungsten, molybdenum, mangancse, silver, gold, and various mixtures including copper-cobalt, coppeniron, copper-chromium, nickel-chromium, cobalt-chromium, manganesechromium, manganese-iron, platinumdron, platinum-cobalt, platinum-nickel, palladium-iron, palladium-cobalt, palladium-nickel, palladium-copper, palladium platinum, palladium-coppcr-cohalt, platinum-copper cobalt, copper-cobalt-nickel-palladiurn, platinum-palladiun -cobalt, etc.

As hereinabove set forth, the catalytically active metal lic component or components are desirably compcsited with a refractory inorganic oxide, the latter serving as a carrier material therefor. Although greater stability and activity are usually obtained When the refractory inorganic oxide contains at least a portion of alumina, other suitable refractory inorganic oxides may be employed including silica, boria, titania, zirconia, hafnia, and mixtures of two or more. The carrier material may be manufactured by any suitable method including separate, successive, or co-precipitat-ion methods of manufacture. The carrier material may comprise naturally occurring substances such as clays or earths, and may or may not be activated prior to use by one or more treatments including drying, calcining, steaming, or particular treatments with inorganic and organic reagents.

The catalytically active metallic components, hereinabove set forth, may be added to the carrier material in any suitable, convenient manner. The catalytically active metallic components may be combined with the carrier material by separate, simultaneous, or successive precipitation methods, .or by impregnating the carrier material with a soluble salt of the catalytically active metal. For example, when platinum is employed, it may be added to the carrier material by commingling the latter with an aqueous solution of chloroplatinic acid. Other water-soluble compounds of platinum, or of other noble metal components, may be utilized within the impregnating solution. When the catalyst is to contain other metallic components, the catalyst may be prepared by com-mingling soluble compounds of these components, particularly the nitrates, chlorides or carbonates, and soaking the particles of the inorganic refractory oxide therein, followed by heating to form the corresponding oxides of the metallic components. When impregnating techniques are employed, there may be one or more impregnating solutions containing one or more of the catalytically active metallic components. For example, When the catalyst is to contain both. platinum and cobalt, the platinum may be impregnated within the carrier material, subsequently calcined, followed by a second impregnating technique incorporating the cobalt component. Although the precise means by which a metallic component is combined with a refractory carrier material is not known, it is believed that it exists in some physical association or chemical complex there-with. Thus, platinum may be present as a free metal, or as a chemical compound or in physical association with the carrier material, or with the other catalytically active metallic components, or in some combination with both. Many methods of preparing such catalytic composites exist and are well known in the prior art; these need not be described in detail herein since no claim is being made for any particular method of manufactur ng the conversion catalyst.

'The sphere of application of the present invention having been set forth, the instant regeneration technique will now be described more explicitly. After the spent catalyst has been exposed to contact with lead-containing exhaust gases under conversion conditions for sufficient time as to become substantially deactivated, whic may occur after anywhere ffOrr about 1,000 to about 26,660 equivment road miles of use, it becomes necessary to regenerate or reactivate it. e

As hereinabove set forth, the regeneration is effected by contacting the catalyst with an aqueous solu.-on of a synthetic detergent or surfactant. The synthetic detergents contemplated for use in this invention may be broadly classified in three groups: (1) anionic detergents the hydrophobic group of which is negatively charged; (2) cationic detergents the hydrophobic group of Which is positively charged; (3) non-ionic detergent which do not ionize.

Representative of the anionic detergents are the organic sulfonates, and sulfates, particularly the alkyl-, aryland alkylarylsulfonic acids and the alkali metal and ammonium salts thereof; the alkali metal sulfates of straight chain primary alcohols such as sodium hendecyl sulfate, sodium lauryl sulfate, sodium cetyl sulfate, sodium stearyl sulfate, etc., and the alkali metal sulfates of monoglycerides such as sodium glyceryl monolaurate sulfate.

The cationic detergents are exemplified by the quaternary ammonium halides containing a long-chain alkyl group, such as dimethyl-ethyl-octadecyl-ammoniurn bro mide and the dialkyl benzotriazoliurn halides such as l-lauryl-S-ethylbenzotriazolium bromide.

The non-ionic detergents includes fatty acid esters of polyglycols such as pentaerythritol monostearate and monolaurate, the glycol esters of fatty acids prepared by treating the acid with ethylene oxide, etc.

The preferred detergents are the arylsulfonic and alkylaryl sulfonic acids and salts thereof because of their present wide availability and low cost. Specific examples of this class of compounds which are highly satisfactory in the practice of this invention are benzene sulfonic acid, ortho-benzcnedisuifonic acid, meta-benzenedisulfonic acid, para-benzenedisulfonic acid, 1,2,3-benzenetrisulfonic acid, 1,2,4-benzenetrisulfonic acid, 1,3,5-benzenetrisulfonic acid, ortho-toluenesulfonic acid, meta-toluenesulfonic acid, para-toluenesulfonic acid, the several toluene disulfonic acids, the several toluene trisulfonic acids, the ortho-xylenesulfonic acids, the meta-xylenesulfonic acids, the para-xylenesulfonic acids, the ortho-xylenedisulfonic acids, the meta-xylenedisulfonic acids, and the para-xylenedisulfonic acids. These acids may be used in the free state as such, or sodium, potassium, or ammonium salts or acid salts of the aryland allrylarylsulfonic acids may instead be employed.

The aqueous solution employed for regeneration may contain two or more different detergents, and may be acidic, neutral or basic. The detergent concentration is not particularly critical and may range from quite dilute up to the limit of saturation at the solution temperature. Excellent results have been achieved with solutions containing from about 0.5% to about 10% by Weight of detergent. The temperature of the solution may range from ambient up to about 2"0 F. or more. The spent catalyst may be contacted with the solution for a period of from 10 minutes to 3 hours or more; the solid-liquid contacting may be accomplished batchwise in a treating vessel, or continuously in a co-current or counter-current contacting tower or moving belt-type apparatus, or in situ by providing the converter with suitable flushing connections for passing the regenerating solution therethrough. Following the treatment with detergent solution, particularly where the solution contains alkali metal ions, is usually desirable to Wash and filter the freshly treated catalyst one or more times. After the catalyst is Washed and filtered, it may be dried or calcined at a suitably high temperature, for example, at a temperature of from about 660 F. to about 800 F. or higher. Such drying may be accomplished by ordinary heating means such as a furnace-or the Wet, freshly treated catalyst may be dried in situ by passage of hot exhaust gases through the converter bed incidental to the normal operation of the catalytic converter.

The following examples are given for the purpose of illustrating the method of the present invention and to indicate the benefits afforded through the utilization thereof. V It is not intended that the present ited to the reagents, concentrations, and/or conditions employed within the examples.

invention be lim- 7 EXAMPLE I A spherical catalyst comprising 0.2% Pt and 10% CO by weight deposited on a refractory oxide base consisting of 2% silica and 98% alumina by weight was contoluene-trisulfonate by weight and maintained at about 150 F. The treated catalyst is then washed and dried and, when employed in a catalytic muffler, will show a substantial improvement in exhaust gas oxidation activity.

taminated with lead by prolonged exposure to lead-con- EXAMPLE III taming exhapsi tmanatmg from an miemal A spent lead-contaminated catalyst having an original bustlon engme using i fuel A portion of this (unleaded) composition of 0.5% Pt and 20% CuO on a leacllled g g i i silica-alumina base may be contacted for 2 hours with a eac ,Welg mg a out grams eslgpate heated aqueous 3% solution of potassium para-xylenesulfi g fatalystc 5331111316 i g i f l0 fonate. The treated catalyst is then removed from the e 2 t yst sainp e f 3%??? solution, washed with water, filtered, and dried for 2 hours a ours. a empera ure 0 m at 900 F. The resulting regenerated catalyst, when fg q f i g% grarfns i 'g q gfi contacted with a mixture of air and exhaust gases at an am Ve F O 0 Owing Tea elevated temperature, will have a substantially improved ment the sulfonic acid solution was decanted and the la exhaust Gas Oxidation activity treated catalyst washed 4 times with 100 cc. volumes of b water. The washed catalyst was then dried and ignited E AM' 1V m a mufiie furnace for 1 w F wuou A catalytic composite comprising 0.75% Pt and 10% Catalyst sample B was similarly treated exce t tha the V 0 by weight impregnated on an alumina-zirconia base meta-benzenedisulfonic acid solution was made basic by having the form of sphsres is emnloyed for th6 Cata addmon thereto of pydmxlde' lytic oxidation of plumbiferous exhaust gases emanating Catalyst Sample, C w slmllarly,treated except that from an internal combustion engine, using leaded fuel. para-toluenesulfonic acid was substituted for the met-a- The average power Output of the engine is 41 brake horse benzenedlwifomc acldpower at 2500 r.p.m., and after 60 hours operating time the The activity of the untreated and treated catalysts, as 2;) catalyst is nearly completely daacfivated. The Catalyst W Q that of fresh catalyst Was tested y mcasufmg the is then unloaded from the converter and placed in a treat- 'lgmtlon temRerature 1 9 temperature use Obtamed by ing tank containing an 0.5 aqueous solution of pentapasage of confammg benzene vapor uncle? Stand erythritol monostearate. The catalyst is treated for 3 ardized cond1t1ons,-1nto and through an apparatus in which hours at tha Solution than decanted and the abed of catalyst was gradually heated until ignition of the lyst Washed, filiarad and dried. The resulting regem benzene :vapor occurred (as indicated by a tempera erated catalyst will now show increased hydrocarbon an differential between bed inlet and bed outlet). A small Carbon monoxide Conversion activity temperature rise and/or a high ignition temperature in- I claim as my invention: dicate a low conversion activity; a correlative evaluation A method of regenerating a lead contaminated cata of catalyzitic mufliers operated on both test automobiles lytic comphsitfi of a refractory inorganic Oxide support ynamometer glands has Show? h a catalyst and a catalytically active component comprising at least sub ected to the foregoing benzene oxidation test must one element Selected from the group consisting of groups have an ignition temperature of less than about 600 F. V A VIA and VH1 f the periodic table, which method a temperature Ilse above abqut to ptil'fofm 40 comprises contacting said composite with an aqueous solusatlsfactoflllf an exhaust gas OXldatlOIl Catalyst tion consisting essentially of water and from about 0.5% The conditions of treatment of the deactivated catalyst to about 10% by weight of a synthetic detergent at from and a comparison of the activities of fresh catalyst, spent ambient temperature to about 200 F. and for a time catalyst, and regenerated catalyst as shown in Table I. period of from about 10 minutes to about 3 hours, where- T able 1 Activity before Reactivating Treatment Activity after Reactivation Wt. Reactivation Wt. Percent Catalyst Sample Pcr- Lead cont Ignition Temp. Gms. Conafter Ignition Temp. Lead Temp, Rise, Reagent Reagent tacting Reacti- Temp, Rise,

F. F. per 100 time, ration F. F.

00.1120 Hours 0 400 600 17.5 1000 0 In-benzcncdisultonic acid 2 2 5.5 400 455 17 5 l000 0 ni'be\1TiiIer(idisul0nic acid 2 2 15.3 425 375 'l 17.5 1000 0 p-tbluen csulfonic acid, 2 2 7.0 365 480 It will be seen from the data of Table I that all three catalyst samples A, B and C, were substantially reactivated. While a greater degree of lead removed may be effected by employing an acidic solution, as demonstrated by samples A and C, it will in many instances be desirable to employ a basic solution, as exemplified by sample B; here, although only about 13% of the original lead was removed, yet the temperature rise of the regenerated catalyst was restored to more than of its original value. The use of detergent solutions which are neutral or basic is most advantageous where the catalyst base or activator is highly susceptible to'acid attack.

EXAMPLE II A lead-contaminated catalyst having an original (unleaded) composition of 1% Pt plus 1% Pd by weight'on a silica-alumina-zirconia base may be treated for 1 hour with an aqueous solution containing 5% trisodium 3,4,5-

by to restore a substantial part, at least, of the activity of the catalytic composite, separating the thus treated composite from said solution and drying the same.

2. A method of regenerating a lead-contaminated catalytic composite of a refractory inorganic oxide support and a catalytically active component comp-rising at least one element selected from the group consisting of groups IB, VA, VIA and VII-I of the periodic table, which method comprises contacting said composite with an aqueous solution consisting essentially of water and from about 0.5% to about 10% by weight of an arylsulfonic acid at from ambient temperature to about 200 IF. and for a time period of from about 10 minutes to about 3 hours, whereby to restore a substantial part, at least, of the activity of the catalytic composite, separating the thus treated com posite rom said solution and drying the same.

3. A method of regenerating a lead-contaminated catalytic composite of a refractory inorganic oxide support ad a catalytically active component comprising at least one element selected from the group consisting of groups IV, VA, VIA and VIII of the periodic table, which method comprises contacting said composite with an aqueous solution consisti lg essentially of Water and from about 0.5% to about 10% by Weight of a salt of an ar'ylsulfohic acid at from ambient temperature to about 200 F. and for a time period of from about 10 minutes to about 3 hours, whereby to restore a substantial part, at least, of the activity of the catalytic composite, eparating the thus treated CG: osite from said solution and drying the same.

4. The method of claim 2 further characterized tliat said acid is an arylmonosulionic acid.

5, The method of claim 2 further characterized that said acid is a toluehesuiforiic acid.

6. The method of ci 2 further characterized that said acid is para-toluenesulfonic acid.

7. The method of claim 2 further characterized in that said acid is an arylpolysulfonic acid.

8. The method of claim 2 further characterized in that said acid is a berizenedisulfonic acid.

9. The method of claim 2 further characterized in that said acid is meta-benzenedisulfonic acid.

1%. The method of claim 3 further characterized in that said salt is an ammonium arylpolysulfonate.

ll. The method of claim 3 is further characterized in that s id salt is ammonium meta-benzenedisulfonate.

12. The method of claim 1 further characterized in that said catalytically active component comprises platinum.

13. The method of claim 1 further characterized in that said refractory oxide support comprises almina.

References Cited in the ile of this patent UNITLD STATES PATENTS 

1. A METHOD OF REGENERATING A LEAD-CONTAMINATED CATALYTIC COMPOSTIE OF A REFRACTORY INORGANIC OXIDE SUPPORT AND A CATALYTICALLY ACTIVE COMPONENT COMPRISING AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF GROUPS IB, VA, VIA AND VIII OF THE PERIODIC TABLE, WHICH METHOD COMPRISES CONTACTING SAID COMPOSITE WITH ANQUEOUS SOLUTION CONSISTING ESSENTIALLY OF WATER AND FROM ABOUT 0.5% TO ABOUT 10% BY WEIGHT OF A SYNTHETIC DEGERGENT AT FROM AMBIENT TEMPERATURE TO ABOUT 200*F. AND FOR A TIME PERIOD OF FROM ABOUT 10 MINUTES TO ABOUT 3 HOURS, WHEREBY TO RESTORE A SUBSTANTIAL PART, AT LEAST, OF THE ACTIVITY OF THE CATALYTIC COMPOSITE, SEPARATING THE THUS TREATED COMPOSITE FROM SAID SOLUTION AND DRYING THE SAME. 